A locking arrangement for vehicle seats is disclosed in PCT-WO 95/17317. With that locking arrangement, it is possible to displace two displaceable parts of the vehicle seat relative to one another continuously. A basically reliable locking is realized, even in the case of increased stress load.
In that locking arrangement, the ratchets have a wedge shape, as required by the obliquely arranged engagement surfaces. The inclined surfaces are pointed downward in an alignment transverse to the displacement alignment. A load in the direction of displacement, when the occasion arises consequently, has such low force components on the ratchets for producing a release of the locking that as a result generally no involuntary unlocking can occur. With a considerable unfavorable introduction of force, as, for example, can occur in the case of a crash with high frequency vibrational fractions, the ratchet in turn is raised out of its locked position, and thus, can be subject to a partial longitudinal thrust, lasting until the next ratchet can take over the load.
EP-A-0 786 37 discloses an arrangement for manual longitudinal adjustment of a vehicle seat. It includes a guide frame, a locking member displaceable vertically therein and a pivotal locking lever within an opening in the locking member. The locking member is provided at the bottom with a cog arrangement projecting downward through an opening in the guide frame and engaging with a corresponding cog arrangement. The guide frame is fastened to a top rail and serves as stop for two springs which act upon the locking member or the locking lever on the locking position. With this arrangement, it is possible only to bring ratchets in the sense of strips of cogs in or out of engagement with one another for the execution of a locking or unlocking setting. In the case of high frequency vibration fractions in the case of a crash, there exists the possibility of the breakdown of the locking.